MySQL检查是否存在外键约束

Question

如果我有：

create table order_items
( 
  orderid int unsigned not null references orders(orderid),
  isbn char(13) not null,
  quantity tinyint unsigned,

  primary key (orderid, isbn)

);

如何检查orderid int unsigned not null references orders(orderid)外键是否存在？

Answer 1

您可以这样使用INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS：

SELECT *
FROM information_schema.REFERENTIAL_CONSTRAINTS
WHERE CONSTRAINT_SCHEMA = '<schema>'
AND REFERENCED_TABLE_NAME = 'order_items'
AND CONSTRAINT_NAME = 'orderid'